1. Field of the Invention
This invention relates to sound reproducing apparatus, and more specifically to a phonograph of the type wherein mechanical vibrations set up in a reproducing stylus by the undulations of a record groove are transmitted directly (i.e., without the process of electrical amplification) to a speaker diaphragm, causing same to generate audible vibrations of the air. Still more specifically, the present invention deals with such a phonograph for particular use with what are herein termed "record cartridges", by which are meant sheet-like holders having disc records attached thereo, but with no unnecessary limitations thereto being intended.
2. Description of the Prior Art
There have been proposed several phonographs of the type for use with record cartridges, among them being Japanese Patent Application No. 46-31762 and Japanese Utility Model Application No. 49-46395. Such prior art devices are mostly unnecessarily complex in construction, difficult of manufacture or assemblage, expensive, and not sufficiently durable. These drawbacks are overcome, to some extent, in Japanese Utility Model Application No. 47-80766 (Publication No. 51-31612).
According to the last mentioned application, however, a speaker cone is mounted eccentrically on a turntable and makes direct sliding contact with a tone arm for receiving therefrom the sound-producing vibrations of a stylus. This arrangement makes the phonograph bulky in size. Furthermore, during rotation of the turntable, the speaker cone mounted eccentrically thereon can be thought of as periodically moving toward and away from the listener, so that the quality of the sound reproduced is adversely affected by the Doppler effect.
The eccentric arrangement of the speaker cone with respect to the turntable has an additional disadvantage arising from the fact that the center of gravity of the turntable-and-cone assembly is out of register with the axis of rotation of the turntable. As a consequence, it is difficult to hold the stylus on the tone arm, which is pivotally mounted on the turntable, in correct engagement with the spiral sound groove of the record cartridge throughout the course of playback, so that the sound stored in the record groove may not be reproduced correctly. The useful life of the phonograph itself may also be substantially shortened.